Michael,
i just hooked up a Korallin 1502 calcium reactor that I picked up used from a person getting out of the hobby. I'm still getting it dialed in, so I cant quite give you a full report on it yet.
Before I got the reactor, I used Seachem's Reef Builder for Alk, and the Reef Advantage for calcium. I also dosed Kalk for quite awhile to add calcium and increase the pH of the tank.
I would suggest you look around for used reactor set ups. If you're comfortable with the DIY mode, go for it. If you'd rather buy one, The Geo is a great reactor and was what I intended to purchase originally, until I stumbled onto mine.
The thing to keep in mind with your set up is that you're not going to need a reactor for awhile. You'll most likely get by with using a two part additive or dripping Kalk. It wasnt until I added my Derasa clam that I really started running through the calcium and alk additives.
Nick